When filling a grain bin, typically the bin opening at the top of the bin must first be opened so that the discharge of a grain conveyor can be aligned with the opening and discharge conveyed material into the bin. Due to the considerable height of the top of the grain bin, various linkages are known to allow users to open a lid spanning the bin opening using a cable or tether connected between the lid and the ground through the linkage.
Examples of tethered linkages for opening a grain bin lid are disclosed in U.S. Pat. No. 4,208,839 by Candy, Sr.; U.S. Pat. No. 4,327,522 by Meadows; U.S. Pat. No. 4,747,244 by Christianson; and U.S. Pat. No. 4,598,496 by VanDaele. In each of these examples however, the linkage is only able to open the lid through a range of approximately 90 degrees. Accordingly the lid extends upwardly above the bin opening and can readily become damaged by contact with a discharge of a conveyor while attempting to align the conveyor with the bin opening.
Canadian Patent No. 1,290,913 by Koenders discloses a bin lid which is displaced generally laterally form the closed position to the open position. Due to the lateral motion require by the linkage to open the lid, it is difficult to provide a mechanical advantage to the opening motion such that the lid can be difficult to open at times.
U.S. Pat. No. 5,218,784 discloses a further example of a bin lid operating by a linkage to open the bin lid. A lever arm supports pulleys thereon such that the cable can be connected directly to the lid member while the lever arm acts to redirect the pulling force on the cable. The linkage requires alignment of the cable with the pulleys which must be well maintained otherwise the cable may become misaligned with the pulley so that the linkage is no longer effectively at operating the bin lid between open and closed position.